76
Journal of Medicinal Chemistry, 1971, Vol. 14, No. 1
INHIBITION B Y P L A T I N U C MO M P L E X E S
Anal.9 (Rb2PtBrl.H20): lib 24.3, Pt 24.7; P t 27.7.
27.7. Found:
Rb
Dibromo(ethylenediamine)platinum(II).--PI( Eir)Ur2, prcpared by the direct, reaction of equiv amount5 of RbnPtBr4.H20 and Eli in ay solutioii at pH 9. The experimeiitally deterniiiied Pt, conteiit, of the complex (46.75:) w a ~iti good ayveenieiit with the theoretical value (47.0 Bromo(diethylenetriamine)platinum( 11) bromide, iPt(L)ieii)RrIBr, was prepared and analyzed 3 s described i i r a previous publicatiori.lD Leucine Aminopeptidase.-The method of XIoseley ~ i i d Xlelius3 was employed to prepare aq enzyme solii. Ploteiii W I I tents of enzyme prepris were estimated by the colorimetric procedure of 3Iiller.11 Assays of enzyme activity were performed by titrating NIla liberated from the hydrolysis of L-leuciiiamide using a Radiometer titrator, Type I11 l e with a Titrigraph, Type SBRLC and syringe buret as a pII-Stat. All assays were carried out at pH 8.0 and 37". A unit of enzyme activity hydrolyzed 1 equiv of L-leucinamide/miii at a 0.01 31 substrate concn.
KBR
(9) Analytical procedures: E. D. Smith, J. A . McCann, and .J. E . Teggins, ibid.. 8, 1872 (1969). (10) J. E . Teggins and D. S.Martin, Jr., itid., 6, 1003 ( I Y O i ) . (11) G. Miller, Anal. Chem., 31, 964 (1959).
0
IO
20
30
40
50
Some Pyrrolidine Derivatives as Antispasmodics
HOURS Figure 2.-Inhibition of P t complexes. Four flasks contaiiiirig 0.05 M MgCl2, 0.025 M barbital buffer, pH 8.0, 20 pl of enzyme and the P t complex or KBr standard, were placed in 37" water bath and aliquots were removed a t various times and added to the assay vessel containing 0.05 121 MgC12, 0.025 M barbital buffer, p H 8.0, and 0.01 11.1 leucinamide.
(Dieii)Br+, which only coiitairis a single Br- ligand, did not deactivate the enzyme completely under the esperimental conditions. It is Jvell known that bidentate ligands, which are bound to the metal through tx-o nucleophilic sites, are much more stable than comparable monodentate ligands. Thus, ethylenediamine complexes of Cu(I1) have considerably larger formation constants than S H , complexes.' I t is possible, therefore, that only Pt complexes which have at least 2 replaceable groups can be bound strongly to the enzyme with resultant deactivation. Sonbiological reactions in which a molecule containing cis nucleophilic groups displaces 2 halide ligands in a Pt(I1) complex to produce a stable product have been reported.8 It is also noticeable that all of the Pt complexes which have been shown t o possess tumor-inhibiting properties by Rosenberg, et d.,* contain labile cis dihalide ligands. JIechanistic similarities between the enzyme-inhibition, tumor-inhibition, arid inorganic substitution reactions are quite possible. Experimental Section Rubidium Tetrabromoplatinate(II).-KZPtBrc was prepared by dissolving P t wire in aqua regia, evaporating the resultant s o h almost to dryness after the addition of excess HBr, and precipitating the hexabromoplatinate (IT) ion in the form of its K salt by the addition of sufficient KzC03to neutralize the remaining acid. A soln of KzPtBi-4 was obtained by reduction of KZPtBra with an equivalent quantity of an aq oxalic acid. The sparingly sol Rb~PtBr4was pptd from this soln by addn of excess RuBr. (7) L. A . Sillen, E d . , "Stability Constants", Chemical Society, London, 2nd ed, 1964. (8) J. V. Rund a n d F. A. Palocsay, rnorg. Chem., 8 , 524 (1989).
JOHS
K. SVGDI:K* AND
~~OHIXDC SINGII I~
School of Pharmacy, City of Leicester Polytechnic, Leicester, England Received June li), 1970
Potent analgetic activity has been reported in N substitut ed-4-aminopiperidine derivatives,1--3 in which the basic heterocyclic S is separated from an acylated anilino group by 3 C atoms. I t n-as considered pertinent to prepare a series of N-(wbstituted phenyl)-N'(1-phenethyl-3-pyrro1idiii;rl)acetamides(1) having this structural feature. The amides 1 were prepared by a 4-stage synthesis (Scheme I) described in the Experimental Section. Kone of the compounds examined showed :my analgetic activity, but they had potent antispasmodic activity in the Iionzett-Rossler test . 4 Fifteen compourids of type 1 were tested against -4cCh, histamine, and 5-HT in anesthetized guinea pigs, the results are presented in Table I. Potent activity is found in compounds where It1 is an unsubstituted aromatic ring. Substitution of the aromatic ring reduced the antispasmodic activity, electron-donating groups producing a less marked reduction in activity than electron-withdrawing groups. The nature of the alkyl group It, influenced the toxicity as well as the activity of the compounds. When R, was Me, activity was maximal and toxicity minimal; the reverse was true when Rzwas E t . The other groups tested at Rzshowed intermediate levels of toxicity and activity. The phenethyl side chain mas selected in view of the associations with potent analgetic a ~ t i v i t y . ~All the compounds 1 showed significantly greater activity (1) P. -1.J. Janssen, British P a t e n t S o . 917,078 (1961). (2) P . A . J. Janssen, Brit. J . Anaesth., 34, 260 (1962). (3) N. J. Harper and C. F. Chignell, J . M e d . C h e m . , 7, 729 (1964). (4) H. Konzett and R . Rossler, d r c h . E z p . Path. Pharmacal., 191, 7 1 (1940).
Journal of Medicinal Chemistry, 1971, Vol. 14, No. 1 77
NOTES
TABLE I N-(SUBSTITUTED PHENYL)-N'-(1-PHENETHYL-3-PYRROLIDENYL)BMIDES Percentage reduction responsea-Hista&HydroxyAcCh amine tryptamine --n i
No.
Yield (%)
1
78
146-147
2
45
118-119
3 4 5 6 7 8
58 41 42 50 45 60
175 220 220 240 210 210
9
60
210 (1.5)
10
11 12
62 42 46
220 (2) 190 (6) 180 (7)
13
60
240 (5)
14
45 39
230 (3) 240 (3)
15
Mp or bp ("0(mm)
Method
Dose (mg/kg iv)
A
(2.5) (3) (2) (3) (0.4) (4)
a Koneett-Rossler test. Isolated as the oxalate, recrystd from EtOH-EtzO. PrOH. All compounds were analyzed for C, H, N.
c
5 100 100 100 2.5 8 0 31 A 5 Animal died 95 100 100 2.5 93 100 B 10 15 83 90 B 10 2 38 0 A 10 (i.p.) 0 4 11 0 B 5 83 100 B 5 76 100 100 100 B 5 2.5 100 100 100 0.1 28 0 28 B 5 83 100 100 1 0 67 42 B 5 51 76 100 B 5 0 68 70 A 5 83 74 100 1 20 12 87 A 5 Animal died 1 0 9 74 5 20 90 100 A A 5 Animal died 1 0 13 60 Isolated as the oxalate, recrystd from EtOH-i-
TABLE I1 Yield
Mp or bp
R
(%)
("0(mm)
Method
CaHs 4-ClCeH4 4-Cl-2-CH3CeH3 4-CH3CsH4 4-OC2HsCaH4
87 53 63 68 81
150-151 151-152 132-133 154-155 159-160
B B B B
2-OCH3CeH4 4-ClCeH4CHz CeHs(CHz)z
53 62 40
240 (1.5) 109-110 14-17
B
B
A A
Recrystn solvent
MEK MezCO EtOH MeOH-MEK CHC13-petr ether (bp 4040') Me2CO-H20 Petr ether (bp 40-60')
See footnote d, Table I.
against histamine and 5-HT than against AcCh. Compounds 2, 13, and 15 were exceptionally toxic within this series, toxicity being manifest as respiratory depression. Antispasmodic activity and respiratory depression have been noted as side effects of m e ~ e r i d i n e . ~ I n an attempt t o explain the absence of analgetic activity in the amides 1, molecular models were made of some related known analgetic^.^ These models showed a substantial degree of coplanarity between the basic heterocyclic N and the aromatic ring attached to the amido group. This feature was absent in the models of amides 1. Beckett and Casy6 postulated that it was essential for the basic center and the aromatic ring to be coplanar for the molecule to have meperidine type analgetic activity, (5) C. 0. Wilson and 0. Gisvold, "Textbook of Organic Medicinal and Pharmaceutical Chemistry," Lippincott, Philadelphia, Pa., 4th ed, 1962, p 563. (6) A. H. Beckett and A. F. Casy, J. Pharm. Pharmacol., 6 , 986 (1951).
I n comparing the amides 1 with analgetics based on 4-aminopiperidine it is evident that reducing the size of the heterocyclic ring from 6 to 5 members, while maintaining the same number of C atoms between the basic center and the aromatic ring, abolishes analgetic activity
.
Experimental Section Uv, ir (Nujol), and nmr (Mersi) spectra were measured for all compounds and were as expected. Melting points were taken on a Biichi apparatus and are uncorrected. N-Phenethyl-5-oxo-3-pyrrolidinylcarboxylicacid (2)was prepared by the method of Paytash, et ul.: from itaconic acid (1.3 g, 0.01 mole) and phenethylamine (1.3 g, 0.01 mole), recrystd from aq DMF: mp 187-188'; yield 1.97 g (97%). Anal. (Ci3H15NOz) C,H,N. N-Phenethyl-5-oxo-3-pyrrolidinylcarboxarnides (3).--N-Phen(7) P. L. Paytaeh, E. Sparrow, and J. C. Gathe, J . Amer. Chsm. SOC., 7'2, 1415 (1950).
78 Journal of Medicinal Chemistry, 1971, Vol. 14, S o . 1 SCHEME
1
NOTES
2,2'-Dialkoxybenzhydrylanlides and 2,2'-Dialkylbenzhydrj 1 Esters of N,N-1)isubstituted a - h i i n o Acids. Synthesis and Pharmacological Evaluation
K.CO
I
vCH---"; I I
CH,CH,Ph
1
0
I
CHuCH2Ph 2
Isomers of lidocaine nhicli do not have t n o Me groups ortho to the anesthesiophore group differ markedlj in anesthetic properties Obviousl) the coii. L 1 siderable steric hindrance pla3 b ail importaiit role i n 0 this pharmacological activit) . A\loreover,the rcplaceI CH,CH.Ph ment of a functional S H by 0 can lead t o isosteric CH-CH-Ph compounds of similar propertiex? 3 4 The title compounds were chosen for i t u c l j because 4a, R, = Ph 4b R, = PhCH-CH-CHthe) coiitaiii :L he\ structural feature of lidocaine. Reagents 1 = SOCIz, 11 = ll??jH2,in = LAH, iv = I ~ z C O C ~ steric hindrance, i1ioieovci I\ e TI eie interested in stud! irig what effect replacement t ~ fSHCO IIY 0'20 in thii ethyl-5-oxo-3-pyrrolidiilylcarboxylic acid (126 g, 0.5 inole) ill t j pe of molecules I\ ould have OII the actil it\ profile CHC13 (200 ml) was added to freshly distd HOC12 (250 g, 2.1 of the iriterniedi,ite h:do esteib J\ :ii mole). The reaction mixture was heated under reflux for 2 hr. mildlj basic condition* .Ittempts to The solvent and unreacted SOCl? were evapd under reduced preparc them 1)) \)oiling (11-o-t 011 lcarhiriol and CIC'Opressure arid the residual oil used without further piirificatioii. CH,Cl 11ere iiii~ucce+fuI. til-o-t 011 Ichloroiiiet1-i,tne4u :i+ Preparation of Amides. Method A.--Arniiles and .Y-pheiiethy1-5-oxo-3-pyrrolidinylcarbonyl chloride in equimolar qiiaitobtiiined tities were allos-ed t o react in an excess of Zc; XaOII. A solid * h i attempt \ \ a s made to coirelate 1oc:d ,mesthet IC sepd on cooling, this x a s collected, washed (H?O),and recrystd. poteiic\ n i t h the bond order of the C'O linkage a* nie:iMethod B.-Amines (2.0 moles) and .V-pheiiethyl-5-oxopyrwred by the CO stretching fiequencj . -1pievioub coirolidinylcarbonyl chloride (1.0 mole) were allowed to react ill dry CHCl, at, -60". A solid, which sepd on storage, was collected relation of this t x pe has beeii ieported.' I . mole) were packed into the thimble and extracted. The products Biological Results.. --C'oinpouiidi 1 28 ( ~ r ct ~t + t c d were worked up in the usual way and purified as .iiich or charac101 tlic'ir local n ~ l t ~ i t h ~:ictilit\ ~ t i c :illd thc rcx
